Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

[Merged by Bors] - refactor(group_theory/order_of_element): now makes sense for infinite monoids #6587

Closed
wants to merge 40 commits into from

Conversation

Julian-Kuelshammer
Copy link
Collaborator

@Julian-Kuelshammer Julian-Kuelshammer commented Mar 8, 2021

This PR generalises order_of from finite groups to (potentially infinite) monoids. By convention, the value of order_of for an element of infinite order is 0. This is non-standard for the order of an element, but agrees with the convention that the characteristic of a field is 0 if 1 has infinite additive order. It also enables to remove the assumption 0<n for some lemmas about orders of elements of the dihedral group, which by convention is also the infinite dihedral group for n=0.

The whole file has been restructured to take into account that order_of now makes sense for monoids. There is still an open issue about adding [to_additive], but this should be done in a seperate PR. Also, some results could be generalised with assumption 0 < order_of a instead of finiteness of the whole group.


@Julian-Kuelshammer Julian-Kuelshammer added WIP Work in progress RFC Request for comment labels Mar 8, 2021
Co-authored-by: Eric Wieser <wieser.eric@gmail.com>
@Julian-Kuelshammer Julian-Kuelshammer added awaiting-review The author would like community review of the PR and removed RFC Request for comment WIP Work in progress labels Mar 12, 2021
@github-actions github-actions bot added the merge-conflict Please `git merge origin/master` then a bot will remove this label. label Mar 14, 2021
@github-actions github-actions bot removed the merge-conflict Please `git merge origin/master` then a bot will remove this label. label Mar 15, 2021
src/group_theory/order_of_element.lean Outdated Show resolved Hide resolved
src/group_theory/order_of_element.lean Outdated Show resolved Hide resolved
src/group_theory/order_of_element.lean Outdated Show resolved Hide resolved
Julian-Kuelshammer and others added 2 commits March 16, 2021 18:11
Co-authored-by: Johan Commelin <johan@commelin.net>
src/group_theory/dihedral.lean Outdated Show resolved Hide resolved
src/group_theory/order_of_element.lean Outdated Show resolved Hide resolved
src/group_theory/order_of_element.lean Outdated Show resolved Hide resolved
src/group_theory/order_of_element.lean Outdated Show resolved Hide resolved
src/group_theory/order_of_element.lean Outdated Show resolved Hide resolved
src/group_theory/order_of_element.lean Outdated Show resolved Hide resolved
src/group_theory/order_of_element.lean Outdated Show resolved Hide resolved
src/group_theory/order_of_element.lean Outdated Show resolved Hide resolved
Copy link
Member

@jcommelin jcommelin left a comment

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Thanks 🎉

bors merge

@github-actions github-actions bot added ready-to-merge All that is left is for bors to build and merge this PR. (Remember you need to say `bors r+`.) and removed awaiting-review The author would like community review of the PR labels Mar 17, 2021
bors bot pushed a commit that referenced this pull request Mar 17, 2021
… monoids (#6587)

This PR generalises `order_of` from finite groups to (potentially infinite) monoids. By convention, the value of `order_of` for an element of infinite order is `0`. This is non-standard for the order of an element, but agrees with the convention that the characteristic of a field is `0` if `1` has infinite additive order. It also enables to remove the assumption `0<n` for some lemmas about orders of elements of the dihedral group, which by convention is also the infinite dihedral group for `n=0`.

The whole file has been restructured to take into account that `order_of` now makes sense for monoids. There is still an open issue about adding [to_additive], but this should be done in a seperate PR. Also, some results could be generalised with assumption `0 < order_of a` instead of finiteness of the whole group.



Co-authored-by: Julian-Kuelshammer <68201724+Julian-Kuelshammer@users.noreply.github.com>
Co-authored-by: Eric Wieser <wieser.eric@gmail.com>
@bors
Copy link

bors bot commented Mar 17, 2021

Pull request successfully merged into master.

Build succeeded:

@bors bors bot changed the title refactor(group_theory/order_of_element): now makes sense for infinite monoids [Merged by Bors] - refactor(group_theory/order_of_element): now makes sense for infinite monoids Mar 17, 2021
@bors bors bot closed this Mar 17, 2021
@bors bors bot deleted the order_of_refactor branch March 17, 2021 10:17
b-mehta pushed a commit that referenced this pull request Apr 2, 2021
… monoids (#6587)

This PR generalises `order_of` from finite groups to (potentially infinite) monoids. By convention, the value of `order_of` for an element of infinite order is `0`. This is non-standard for the order of an element, but agrees with the convention that the characteristic of a field is `0` if `1` has infinite additive order. It also enables to remove the assumption `0<n` for some lemmas about orders of elements of the dihedral group, which by convention is also the infinite dihedral group for `n=0`.

The whole file has been restructured to take into account that `order_of` now makes sense for monoids. There is still an open issue about adding [to_additive], but this should be done in a seperate PR. Also, some results could be generalised with assumption `0 < order_of a` instead of finiteness of the whole group.



Co-authored-by: Julian-Kuelshammer <68201724+Julian-Kuelshammer@users.noreply.github.com>
Co-authored-by: Eric Wieser <wieser.eric@gmail.com>
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment
Labels
ready-to-merge All that is left is for bors to build and merge this PR. (Remember you need to say `bors r+`.)
Projects
None yet
Development

Successfully merging this pull request may close these issues.

None yet

5 participants